Dust in dental laboratories. Part II: Measurement of particle size distributions.

It has been demonstrated in a previous study that threshold limit values of various elements or compounds could be considerably exceeded in various work operations in the dental laboratories when appropriate ventilation systems were not used. This refers to working with chromium-cobalt alloys, amalgam dies, porcelain, and gypsum. In the present study, size distributions of particles arising from cutting, grinding, or polishing of alloys, gypsum, porcelain, or denture base material in dental laboratories have been measured. The particle size distributions were evaluated by means of light and electron microscopy as well as by coulter-counting techniques. The measurements revealed the occurrence of a high proportion of respirable dust associated with these operations. consequently, the use of efficient ventilation systems is strictly necessary to ensure industrial safety with respect to air pollution in the working environment of dental laboratories.